A certain complex of metal M is formulated as MCl3 ∙ 3 H2O . The coordination number of the complex is not known but is expected to be 4 or 6.
(a) Would conductivity measurements
provide information about the coordination number?
(b) In using conductivity measurements to test which ligands are bound to the metal ion, what assumption is made about the rate at which ligands enter or leave the coordination sphere of the metal?
(c) Suppose you experimentally determine that this complex exists in aqueous solution as a single species. Suggest
a likely coordination number and the number and type of each ligand.
(a) Conductivity measurements can provide information about the coordination number of a complex if the complex has a different conductivity behavior between a coordination number of 4 and a coordination number of 6. If the complex shows different conductivities under certain conditions, it could indicate a change in the coordination number.
To conduct this test, you would need to measure the conductivity of the complex under different conditions. For example, you could vary the concentration of the complex, the temperature, or the presence of other ions. By comparing the conductivity behavior under these different conditions, you may be able to infer the coordination number of the complex.
(b) When using conductivity measurements to test which ligands are bound to the metal ion, an assumption is made about the rate at which ligands enter or leave the coordination sphere of the metal. This assumption is that the ligands exchange rapidly with each other and the solvent molecules, ensuring a dynamic equilibrium is established.
In other words, it is assumed that ligands can easily enter or leave the coordination sphere without significantly altering the overall conductivity of the complex. This assumption is based on the concept of ligand exchange, where ligands surrounding the metal ion can rapidly interchange with each other in solution.
(c) If the complex exists as a single species in aqueous solution, it suggests that the coordination number is constant and does not vary with the conditions of the solution.
Based on the given information that the expected coordination number is 4 or 6, and the formula MCl3 ∙ 3 H2O, we can make some suggestions. Since the complex is hexaaquometal(III) chloride, it implies that the metal ion is coordinated with six water molecules. Therefore, the likely coordination number is 6. Each water molecule is also a ligand in this case.
Hence, one possible suggestion for the coordination number is 6, and the ligands in this complex would be six water molecules.